There are many different types of sheet-fed printers used in home and office settings. Such printers typically include a printing path including a print media input holder, a print region, and a printing mechanism. As an example, printing mechanisms can include a printhead, such as an inkjet printhead, that deposits marking material on a sheet of recording medium. Such printheads can span the width of the recording medium, so that printing is done a line at a time. Alternatively, such printheads can be shorter than the recording medium, and are moved by a carriage across the recording medium to print an image a swath at a time. As another example, a printing mechanism can include an energy source, such as a laser, which selectively modifies a surface such that toner particles can be attracted to the surface in an image-wise fashion for subsequent transfer to a sheet of recording medium.
In the past, home or office printing was predominantly done on one side of a sheet of recording medium, and then the sheet was discarded when the printed image was no longer needed. For types of recording media where both sides of the sheet are usable, this represents significant waste. More recently, many printers have included duplexing units so that the user could readily print on both sides of a sheet. Still there are many sheets being printed only on one side.
Increasingly, users of printed media in home and office settings have become environmentally conscious and now recycle printed media. A standard type of recycling is to store up printed media that is no longer needed and send it to a processing center where the waste paper is recovered and remade into new paper products. Recycling of one ton of office or copier paper saves about two tons of wood, reducing the need to cut down trees for paper making. An even more environmentally friendly and cost-conscious measure is to reuse paper that has been printed on. U.S. Pat. No. 6,236,831 discloses scanning a previously printed marking surface, determining a location of printing on the marking surface, and depositing an erasing material, such as an opaque white material or a bleaching compound to conceal or remove marks that were previously made. Most printers, however, do not have the capability for depositing an opaque white material or bleaching compound.
An alternative approach is to reuse recording medium that has previously been printed on one side but not on the other side. A user can remove paper from a recycling storage unit, load it into a printer and print on the side that was not previously marked on. A difficulty with this approach is that recording medium in a recycling storage unit is typically not stored in an ordered fashion with the blank sides facing in a uniform direction, but rather is randomly oriented. The user typically needs to manually sort the stack of recording medium before loading it into the printer.
What is needed is a method of providing an indicator on a previously marked on side of sheet of recording medium included in a randomly oriented stack of recording media in order to indicate that the side with the indicator is not the side containing newly printed content.